In the realm of mental phenomena, experiment and measurement have
hitherto been chiefly limited in application to sense perception and
to the time relations of mental processes. By means of the following
investigations we have tried to go a step farther into the workings
of the mind and to submit to an experimental and quantitative treatment
the manifestations of memory. The term, memory, is to be taken here
in its broadest sense, including Learning, Retention, Association and
Reproduction.

The principal objections which, as a matter of course, rise against
the possibility of such a treatment are discussed in detail in the
text and in part have been made objects of investi-gation. I may
therefore ask those who are not already convinced a priori of the
impossibility of such an attempt to postpone their decision about
its practicability.

The author will be pardoned the publication of preliminary results in
view of the difficulty of the subject investigated and the
time-consuming character of the tests. Justice demands that the many
defects due to incompleteness shall not be raised as objections against
such results. The tests were all made upon myself and have primarily
only individual significance. Naturally they will not reflect
exclusively mere idiosyncrasies of my mental organisation; if the
absolute values found are throughout only individual, yet many a
relation of general validity will be found in the relation of these
numbers to each other or in the relations of the relations. But
where this is the case and where it is not, I can hope to decide only
after finishing the further and comparative experiments with which I
am occupied.